Embattled Staten Island Republican Michael Grimm steps down from Congress on Monday, leaving the door wide open for the prosecutor at the center of the Eric Garner case to replace him.

On Friday, top Republican leaders threw their support behind Staten Island D.A. Dan Donovan to succeed Grimm, who abruptly announced he would resign after pleading guilty to federal tax fraud over a health food restaurant he once owned.

Those backers include former Mayor Rudy Giuliani and Staten Island GOP chairman John Antoniello.

A Donovan candidacy would be “a slap in the face to the police reform movement," said Linda Sarsour, a resident of Grimm’s district and a member of Justice League NYC, which helped organize street protests calling for police reform in the wake of Garner’s death.

Justice League NYC has been demanding the arrest of Police Officer Daniel Pantaleo for allegedly killing Garner.

Donovan said last week he’s considering a run for the seat that envelops Staten Island and parts of southern Brooklyn. Gov. Andrew Cuomo has yet to announce details of the expected special election to replace Grimm.

Donovan, who served as an assistant DA in Manhattan and an aide to former Staten Island borough president Guy Molinari, was elected Staten Island D.A. in 2004, and re-elected twice. Donovan ran a failed bid for state attorney general in 2010.

"There's no doubt that the majority of my community will be holding Donovan responsible for his actions in any election he's in," North Shore resident and local activist John McBeth, Sr., a black Democrat told Metro.

Donovan’s critics fault his judgement, including his prosecution of the Working Family Party over charges that it illegally funded the campaign of City Councilwoman Debi Rose, who in 2009 became the first black woman to represent the island.

Donovan recused himself from the case in 2010 and appointed a special prosecutor who is still investigating it.

A spokesman for Donovan did not immediately respond to Metro for comment.

Staten Island is unlike the rest of the city, said political science professor Richard Flanagan of the College of Staten Island. While pockets of Staten Island have a diverse voter base, the borough’s electorate remains largely center-right.

"The reformist rhetoric, outside of the North Shore, goes over like a lead balloon in the middle of the island or South Shore," he said.

Democrats still outnumber Republicans in the district, meaning Donovan is not a shoe-in.

"Staten Island is tailor made for centrist Republicans and Democrats," Flanagan said, leaving the door open for GOP challenges by likely candidates Assemblywoman Nicole Malliotakis and state Sen. Andrew Lanza.

Democratic candidates may include Assemblyman Michael Cusick and former Rep. Michael McMahon.

But McBeth pointed out that Staten Island’s 121,000 or so registered Democrats still outnumber its about 76,250 Republicans, even if those who turned out to vote in November elected Grimm into office three times — most recently while he faced a felony indictment.

“We [Democrats] have the numbers to do it, but we just don't do it when we need to,” McBeth said.